A circuit such as this is disclosed, for example, in EP 1 613 841 B1.
Thermal power stations use thermodynamic cycles to convert heat to mechanical and/or electrical energy. Conventional thermal power stations produce the heat by combustion of fuels, in particular the fossil energy sources coal, oil and gas. In this case, the cycles are operated, for example, on the basis of the classical Rankine cycle, with water as the working medium. However, the high boiling point of water makes water unattractive in particular when using heat sources at temperatures between 100 and 200° C., for example geothermal liquids or waste heat from combustion processes, because it is not economic.
In recent years, widely different technologies have been developed for heat sources with a temperature as low as this, which allow their heat to be converted to mechanical and/or electrical energy with high efficiency. In addition to the Rankine process with an organic working medium (organic Rankine cycle, ORC), the so-called Kalina cycle is, in particular, distinguished by considerably higher efficiencies than the classical Rankine process.
Various circuits have been developed for widely differing applications based on the Kalina cycle. These circuits use a two-substance mixture (for example ammonia and water) instead of water as the working medium, with the non-isothermal boiling and condensation process of the mixture is used to increase the efficiency of the circuit, in comparison to the Rankine circuit.
EP 1 613 841 B1 discloses a Kalina circuit of this type, which is particularly suitable for temperatures from 100 to 200° C., in particular from 100 to 140° C. EP 1 070 830 A1 discloses a further known circuit such as this.
It is already known from conventional water-steam circuits for the steam that is produced to first of all bypass the turbine, in order to start a circuit such as this, until a pressure has built up in the circuit which is sufficient to operate the turbine. However, if this principle is applied to a Kalina circuit mentioned above, then pressure pulsations can occur in the circuit during the starting of the circuit, which can become sufficiently great that an emergency shut-down of the circuit is required.